The instant invention relates to hingeable plate assemblies of the general type utilized for carrying out photolithographic processes and more particularly to an improved hingeable plate assembly and to a displaceable hinge assembly therefor.
Photoglithograph processes have generally been found to be highly effective for use in forming relief patterns on various substrates, such as those utilized in manufacturing printed circuit boards. In this connection, typically a photolithographic process of this type is carried out by applying a mask image to a glass plate, and then overlaying the glass plate on a substrate which has been previously coated with a photosensitive polymer. The unmasked areas of the substrate are then exposed to actinic radiation in order to effect a desired reaction in the photosensitive polymer thereon. Thereafter, the glass plate is removed from the substrate, and the substrate is exposed to a solvent treatment process and/or an etching process in order to produce a desired relief image on the substrate which is either the same as or a mirror image of the mask image on the glass plate, depending on the particular process. Similar processes have been found to be highly effective for simultaneously applying images to both sides of substrates utilizing hingeable plate assemblies comprising pairs of masked glass plates which are hingeably connected together. A process of this type is generally carried out by positioning a substrate between a pair of glass plates having mask images thereon and then simultaneously applying actinic radiation to a photosensitive polymer which has been preapplied to both sides of the substrate. Thereafter both sides of the substrate are exposed to a solvent process and/or an etching process in order to form the desired relief image patterns on the substrate.
It has generally been found that it is extremely important to be sure that a mask image on a plate utilized in a photolithographic process of the above type is precisely aligned with respect to the appropriate surface of the substrate to which the image is to be applied before the surface is exposed to actinic radiation. It has also been found that it is extremely important to be sure that both of the mask images on the plates of a hingeable plate assembly utilized in a process of this type are properly oriented with respect to each other before the surfaces of a substrate which is interposed therebetween are exposed to actinic radiation. In this connection, it has been found that proper image orientation can be particulary critical when utilizing a photolithographic process for forming a substrate for a printed circuit board where an improperly oriented image can cause one or more open circuits, short circuits, or improper resistances.
Unfortunately, the plate assemblies which have been heretofore available for use in photolithographic processes of the above type have generally been found to be less than satisfactory for consistently applying images to the opposite sides of substrates in proper orientations. In this connection, it has been found that it is generally necessary for the hinge mechanisms of plate assemblies of this type to allow the respective plates thereof to be displaced outwardly at least slightly relative to each other in order to enable the plate assemblies to accommodate substrates of different thicknesses. As a result, many of the hinge mechanisms which have been utilized in the heretofore available plate assemblies of this general type have included resiliently flexible elements in order to adapt them so that the plates thereof can be resiliently displaced outwardly relative to each other to varying degrees. However, it has been found that plate assemblies which include resilient hinge mechanisms of this type are generally incapable of repeatably operating with high degrees of precision for aligning images on the plates thereof with respect to substrates. Specifically, it has been found that the resiliently flexible elements in the hinge mechanisms of plate assemblies of this type generally allow the plates thereof to be shifted to misaligned positions wherein the mask images thereon are out of alignment with respect each other.
Plate assemblies representing the closest prior art to the instant invention of which the applicant is aware are disclosed in the U.S. Pat. Nos. to Freiberg 4,412,739; Postupack 4,421,836; Tongel 4,445,775; Bowser 4,446,184; Kenworthy et al 4,584,216; and Emmert 4,600,298. However, while a number of these references have recognized the need for providing an effective plate assembly which is adapted to accommodate substrates of different thicknesses without allowing the plates thereof to be shifted to misaligned positions, they have generally failed to provide an effective solution to this problem. In any event, the devices disclosed in these references fail to suggest the novel structural features of either the plate assembly of the subject invention or the hinge assembly of the subject invention, and hence they are belived to be of only general interest with respect thereto.
The instant invention provides an effective hingeable plate assembly and a displaceable hinge assembly therefor which overcome the disadvantages of many of the heretofore available plate assemblies and hinge assemblies. The displaceable hinge assembly of the instant invention comprises a first hinge piece which is securable to a first member and has an elongated slot formed therein of preferably V-shaped configuration. The hinge assembly further comprises a second hinge piece which is securable to a second member and a pivot member mounted in a predetermined fixed position on the second member wherein it is receivable in the slot in the first hinge piece. The second hinge piece preferably has a socket formed therein, and the pivot member preferably comprises a spherical ball element which is received in the socket in the second hinge piece and in the slot in the first hinge piece, and the first and second hinge pieces are preferably assembled so that the ball element is captured between the first and second hinge pieces. When the hinge assembly is constructed in this manner, the ball element can travel in the slot to enable the second hinge piece to be displaced outwardly relative to the first hinge piece in a direction substantially parallel to the slot, and the ball element can rotate in the socket and/or the slot to enable the second hinge piece to be pivoted relative to the first hinge piece. The hinge assembly further comprises means for obstructing the ends of the slot in the first hinge piece and means for maintaining the first and second hinge pieces in closely adjacent relation in order to retain the ball element in captured relation in the slot and the socket.
The hingeable plate assembly of the instant invention comprises first and second plates and first and second displaceable hinge assemblies of the above described type which are assembled with the plates so that the first hinge pieces of the hinge assemblies are attached to the first plate and so that the second hinge pieces thereof are attached to the second plate. The plates are preferably of substantially flat, rectangular configuration, and the slots in the first hinge pieces preferably extend in substantially perpendicular relation to the first plate. When the hinge assemblies are assembled in this manner, the plates maintain the first and second hinge pieces in closely adjacent relation; and since the slots extend in substantially perpendicular relation to the first plate, the second plate is outwardly displaceable relative to the first plate in a direction which is substantially perpendicular to the first plate, although it is nevertheless hingeable relative to the first plate. The plate assembly of the instant invention preferably further comprises a compressible gasket on one of the plates which is interposed between the two plates when they are received in closely adjacent, substantially parallel relation, and the gasket is preferably adapted so that it defines a frame between the plates. Further, the plate assembly is preferably constructed so that the interior frame defined by the gasket can be evacuated to draw the first and second plates together, and the first and second plates are preferably constructed from a transparent glass.
It has been found that both the hinge assembly of the instant invention and the plate assembly which comprises the hinge assembly can be effectively utilized in connection with photolithographic processes, such as those utilized in the manufacture of printed circuit boards. In this connection, for use of the plate assembly of the instant invention in a photolithographic process, the plates are preferably embodied as glass plates, and photomasking materials are applied to the plates in order to define predetermined mask images thereon. Thereafter, a substrate having a photosensitive polymer on the surfaces thereof is assembled between the plates so that the mask images on the plates are overlaid on the appropriate surfaces of the substrate, and the entire assembly is then exposed to actinic radiation. In this connection, because the hinge assemblies of the instant invention enable the plates to be displaced outwardly with respect to each other while nevertheless maintaining the plates in aligned relation, the plate assembly can effectively accommodate substrates of various thicknesses.
Accordingly, it is a primary object of the instant invention to provide an effective displaceable hinge assembly which is operative with a positive hinging action for hingeably connecting a pair of first and second members together so that the second member is outwardly displaceable along a predetermined path with respect to the first member.
An even further object of the instant invention is to provide a hingeable plate assembly comprising hingeably connected first and second plates wherein the second plate is outwardly displaceable with respect to the first plate along a predetermined path.
An even further object of the instant invention is to provide an effective plate assembly for photolithographic processes which is operative with a high degree of accuracy and repeatability.